DESCRIPTION: This is a study on a putative CMV-encoded superantigen (SAG). The applicant has previously shown that CMV infection induces the preferential proliferation of Vb12 T cells and that HIV preferentially infects SAG activated Vb12 T cells. The goals of this proposal are to identify the CMV-related SAG and to investigate the hypothesis that Vb12-bearing T cells are a reservoir for HIV infection and are resistant to apoptosis. In particular cloned SAG will be used to examine the expression, tissue distribution and homologies of the CMV SAG to other known SAGs and herpesvirus gene products. The investigator will examine the nature of HIV infection in Vb12 T cells as to the frequency of infected cells, their clonality, and whether they produce infectious virus. He will investigate whether SAG-stimulated Vb12 T cells are resistant to the induction of apoptosis and begin to explore possible mechanisms. Another aim is to investigate whether the SAG enhances CMV infection or reactivation. Finally a potential role of the CMV SAG in enhancing HIV infection will be explored.